Containment systems for animals/pets, in particular dogs, have been used for several decades. The most commonly used containment system is the buried wire fence system, which uses a stimulus collar worn by the pet and the containment area is defined by a buried wire. When the pet approaches the buried wire the collar picks up a radio signal. The radio signal is generated by a control box, which is located inside the pet owner's residence and sent through the buried wire. Typically, there is a warning zone close to the boundary and when the pet reaches this zone the collar emits an audible signal. If the pet continues to the boundary, the collar will issue a static correction, hopefully causing the pet to retreat to the containment area.
There are certain inherent deficiencies and limitations with buried wire fence systems. Since these systems require a control box located within the pet owner's home with an uninterrupted power source and a length of wire buried in the ground, installation is difficult and generally requires a professional, which is expensive and time consuming. Additionally, once the installation is complete, the system typically remains buried at the property in the original configuration since removal and/or modification would be very costly.
Another inherent issue is that the buried wires tend to break in geographic regions that have changing seasons, due to freezing and thawing. Broken wires result in failure of the system, potentially allowing the pet to escape. This is particularly problematic since buried wire systems are open loop systems, i.e. they provide no feedback to the pet owner if the pet escapes.
With the limitations of buried wire systems, other animal containment systems which operate wirelessly have been introduced and provide some incremental improvements. These systems solve the problems associated with burying wires in the ground, however they still have a major limitation; namely, they are also open loop systems and do not provide feedback to the owner in the event the pet escapes the containment area.
Wireless systems have other limitations based on how they operate. The general operating principle is that the base station emits a radio signal and the collar detects the signal strength. When a defined low signal level threshold is detected, the collar will emit an audible correction and when it crosses an even lower threshold, the collar will issue a static correction.
The base station projects the radio signal in all directions equally, thus the containment area is always circular in shape. The owner defines the circle size by adjusting a radius dial on the base station, up to a maximum radius. Of course, yards take on various shapes and sizes and with the system being limited to a circular containment area it provides limited flexibility. Additionally, the pet owner must be careful that the signal does not project onto unwanted or undesired areas, such as neighboring yards or, even worse, busy streets. For large yards, multiple base stations may be needed and they must be set up in a fashion that the radio signals overlap in order for the pet to have a common coverage area and thus a pathway to roam between containment areas.
A further limiting aspect of the wireless solution is that the collar receives the radio signal from the base station via Line of Sight (LoS). Because of this, the emitting circle may become irregular in shape based on landscape effects and any object between the base station and the collar. This known phenomenon limits the styles and types of suitable yards to generally flat and clear areas to maximize the full distance of the circle.
Also available on the market is a wireless pet containment system using Global Positioning System (GPS). This system does not require buried wire and does provide more flexibility and customization regarding the containment area. It does however still require a base station and professional installation. The method used in this system is called a Real Time Kinematic (RTK) system, which is comprised of a base and a rover (i.e. collar).
Common in GPS and other satellite systems are the inherent positioning errors that come with the technology. GPS/other satellite system receivers receive and lock onto multiple satellites to determine location on earth. Because the satellites are several thousands of kilometers away, the signals they emit are subject to interference when traveling through earth's atmosphere (ionospheric errors). When the signals reach earth's surface, even more error is introduced by the local environment. Trees, buildings, land, and other objects reflect GPS/other satellite system signals and cause them to propagate differently. This causes delays and polarization effects. Positioning errors of this type are called multipath errors and play a significant role in the overall GPS/other satellite system error budget.
With the RTK system, the base is stationary and can minimize the overall positioning error by using carrier phase tracking. Error corrections are then sent by the base station to the rover/collar to reduce positional error of the collar.
Thus, the RTK system has a stationary reference point and collar reference point and can actively track the distance of the rover from the base station with a high degree of accuracy.
However, there are shortcomings with the RTK system. First, the system requires a professional technician not only to install it, but also to modify any collar or containment area settings thereafter. Additionally, the distance from the base station (and hence the size of the containment area) is limited by LoS and local environmental obstructions. Moreover, the base needs an unobstructed view of the sky as well as an uninterrupted power source to work properly. And, as with the other systems described above, the system is an open loop system and does not provide feedback to the owner in the event the pet escapes the containment area.
In addition to pet containment systems, there has been a rise in pet collar tracking and location devices. Some location devices use cellular technology, which is limited by coverage area and is not very accurate. A preferred technology for tracking the location of pets uses the Global Navigation Satellite System (GNSS). Although, GNSS is not a perfect solution as there are many sources of error that impact location accuracy. While some errors are externally induced by the atmosphere and the local environment, others are introduced by the quality and type of technology used to build the GNSS receiver system.
One of the most critical aspects is the placement and type of antenna used in the GNSS receiver system within the pet collar. Current location and tracking collars are poorly architected and designed using sub-par components and techniques to reduce GNSS errors. Another important aspect is the GNSS receiver's inability to filter out erroneous signals. Large and closely spaced buildings in cities form so called “urban canyons” which cause significant multipath errors that can be upwards of tens or even hundreds of meters. Current tracking collars do not account for such environments and can cause large inaccuracies that misguide pet owners to their pets. In frantic moments, pet owners need accurate technology and techniques to be able to find their pets as efficiently as possible.